The present invention relates to a cooling system used for a package mounting a plurality of heat-generating electronic components such as integrated circuits (IC's) on a substrate.
A prior art cooling system for a package mounting electronic components on a substrate is disclosed in U.S. Pat. No. 4,109,707. The system comprises a micropackage mounting a plurality of IC's on the upper surface of a substrate, a connector connected to the package, and a heat exchanger in contact with the lower surface of the substrate mounting no IC. Liquid coolant such as water flows inside the exchanger. The exchanger is provided with a flexible thin plate on the bottom thereof. The lower surface of the package is not completely flat. In order to efficiently conduct the heat generated from the IC's into the coolant, it is critically necessary to force the flexible plate to come into close contact with the lower surface without clearances therebetween. To obtain such close contact, the system tries to bring the plate in close contact with the lower surface by deforming the plate with the pressure of water circulating inside exchanger.
In the system, the plate provided on the bottom of the exchanger is made of an extremely thin copper sheet having a thickness of 0.05 to 0.25 milimeters in order to obtain superior flexibility. However, since it is made of such a thin sheet of material, the water pressure used to press the plate against the lower surface, which is a determinant factor of the thermal resistance between the plate and the lower surface, cannot be increased to thereby present an impediment in reducing the thermal resistance between the substrate and the exchanger. Because of its weakness, the plate must be handled with utmost care when it is removed from the package at the time of replacement. If the plate is damaged, the water inside the exchanger may leak to malfunction the IC's.